Pontoon boats are popular recreational watercraft that are prized for their ability to carry a large number of persons and a heavy load. Pontoon boats were created at least as early as 1952, when a Minnesota farmer, Ambrose Weeres, assembled the first pontoon boat by attaching a wooden deck to the top of two columns of steel barrels welded together end to end to form a cylindrical pontoon. While the preferred metal for the pontoons may now be aluminum, most pontoon boat companies still utilize Mr. Weeres' simple but obsolete design of wooden decks attached to two cylindrical barrel-shaped pontoons, each having a nose cone and an end cap. It is thus an object of the invention to provide a pontoon boat that improves upon the historical design of a wooden deck attached to a cylindrical pontoon.
Historically, the primary means of improving pontoon boat performance consisted of using a larger motor, which provides more thrust, or adding a third pontoon to the center of a pontoon boat, which reduces drag by giving more pontoon surface area to support the weight of the boat and allowing the boat to float higher in the water. The inventors herein have already made advancements in the field of pontoon boats when compared to the historical art. For example, U.S. Pat. No. 7,188,576, issued to the inventors herein, disclosed a method of constructing a pontoon boat from unique interlocking aluminum planks that improved overall boat performance by reducing weight, lowering deck height, and improving rigidity of the overall structure. While these design changes improved pontoon boat performance, such changes did not address the problems that arise from the continued use of traditional cylindrical pontoons. It is desirable for the performance of pontoon boats that the pontoons generate lift. However, cylindrical pontoons of the prior art generate very little lift because the bottom surface of the cylindrical pontoon is rounded. It is thus an object of the invention to provide improved lift qualities to pontoon design.
A pontoon of the prior art typically has at least three components; a nose cone, a number of barrels joined by circumferential welds, and an end cap. The nose cone is typically constructed by forming two nose cone halves, a right and left half. The respective nose cone halves are then welded together along the vertical axis to form the nose cone piece. The position of the weld seam joining the two nose cone halves together presents a possible leakage point because the weld seam runs the length of the nose cone, thereby extending below the water level. Accordingly, the nose cone weld seam is subjected to water and water pressure as the pontoon boat travels through the water. Further, because the nose cone is the most likely location for damage following any sort of collision, such as by running aground, the weld seam is prone to damage and subsequent leakage. It is thus an object of the invention to provide a pontoon with an improved, single-piece nose cone design that does not require a weld seam joining two nose cone halves that is located at the point most likely to suffer predictable damage.
The body of a pontoon is generally constructed from a number of barrel segments. Typically, a pontoon barrel segment is created from a flat rectangular piece of metal that is shaped into a cylinder and joined by a longitudinal weld seam. A typical pontoon is thereafter constructed of two or more pontoon barrels joined at one or more ends using circumferential welds. The barrel-joining circumferential welds are oriented perpendicular to the length of the pontoon, and when the pontoon barrels are welded together, they form a long cylindrical pontoon body to which the nose cone and end caps are attached using circumferential weld seams. Together, when the unit is completed, it is referred to as a pontoon.
Pontoons should be watertight, and although most modern pontoons are filled with foam or other types of floating material to avoid sinking, even slightly leaky pontoons greatly reduce pontoon boat performance due to the relatively high weight of water. Any weld length is a potential source of a leak for a pontoon. For this reason, it is preferred to situate the longitudinal welds above the water surface. With this method of construction, the only welds that routinely come in direct contact with the water are the circumferential welds that join the barrels and the nose cone and end cap to the barrels.
The circumferential weld joining the nose cone to the cylindrical body also presents a potential structural strength problem because the upward force of the water, the forces caused by running the nose cone area aground, are not spread equally across the entire weld; rather, the upward force upon the nose cone tends to compress or stretch various locations of the circumferential weld. It is thus an object of the invention to alleviate the unequal stresses associated with circumferential welds joining the nose cone to the cylindrical body.
In an attempt to improve upon the cylindrical body designs of the prior art and to address poor planing characteristics of pontoon boats in general, in the last decade the pontoon boat industry began welding to the surface of the cylindrical body one or more longitudinal strakes at or below the water surface. As a pontoon boat is typically powered by a rear-mounted engine, the strakes were designed to direct water downward, thus tending to improve the planing characteristics of the traditional cylindrical body by generating lift. Strakes of the prior art represent a rather crude fix to the known problems because most of the running surface of the cylindrical body remained convex.
The limitations to a convex pontoon design can be illustrated by an analogy to treatment of light by a lens: convex lenses scatter light, whereas concave lenses focus light. In pontoons, convex surfaces scatter water pressure away from all sides of the pontoon, whereas concave surfaces directs water pressure downward, thereby generating lift (the direction of force applied by the pontoon upon the water can described by a vector field). It is thus another object of the invention to provide a pontoon design that maximizes lift.
There are clear drawbacks to using after-applied lifting strakes, because if two strakes are used, then at least four longitudinal welds are typically required. Each of the two longitudinal sides of each strake must be attached to the bottom surface of the pontoon. There are many problems associated with welding strakes to existing pontoons, including that each weld increases the susceptibility of leakage in the pontoon in the event a weld is not within acceptable tolerances. This stepwise manner of construction is also time-consuming because it requires a large number of total weld lengths for the pontoon. That is, on a typical pontoon there are longitudinal welds for the creation of the barrel and at least four longitudinal welds for the attachment of two lifting strakes. It is thus another object of the invention to provide a pontoon design that requires a minimal number of longitudinal welds while at the same time adopting the lift and planing advantages offered by strakes.
While pontoon makers have remained relatively traditional in the shape of pontoon hulls, some inventors have experimented with hull shapes in other types of watercraft. However, the problems presented for distinct types of watercraft are markedly different than those faced by pontoon boats, and accordingly the solutions to such problems are likewise different. For instance, U.S. Pat. No. 3,208,421 (the “'421 patent”), issued to W. K. Landes et al., discloses a seaplane float that changes shape from front to rear to reduce drag. The front part of the float has a main concave channel and two smaller concave channels on each side of the main concave channel. The rear portion of the float has two distinct, flat keel pads. In the '421 patent, the inventors used two concave channels. When the seaplane float is viewed from the side, the front of the float tapers into a narrow, aerodynamic trailing edge. The minimal trailing edge of the seaplane float is made possible because the center of gravity of a seaplane is near the front due to the heavy weight of the engine when compared with the lighter weight of the tail of the seaplane. The concerns for a pontoon boat are opposite the concerns facing the inventor for the seaplane float design. The engine on a pontoon boat is in the rear, requiring substantial rear flotation. It is therefore an object of the invention to provide sufficient rear flotation to accommodate engine weight and thrust typical to pontoon boating.
The design of the hull on the seaplane float depicted by Landes defines a separation between three concave channels along the length of the hull. This design allows the seaplane to advantageously ride on the keels alone during high speed takeoff; yet for an aluminum pontoon boat such a design is impractical and undesirable due to the fact that such keel types would impugn the integrity of the concave running surface. It is therefore an object of the invention to provide a fully concave running surface without flat keels to maximize downward force when the pontoon boat is under power.
Sea planes take off and land at relatively high speeds, which require higher curvature of the center concave channel for maximum convergence of water in the twin rear channels to provide lift. It is thus an object of the invention to provide a pontoon that minimizes drag while at the same time providing ample flotation to support an engine mounted at the rear of a pontoon boat.
U.S. Pat. No. 6,293,218 (the “'218 patent”), issued to R. F. White, provides a concave tunnel-hulled boat that utilizes lifting strakes. Like the seaplane float, the tunnel changes shape from fore to aft; also, the leading edge of the tunnel is formed from two concave channels which tapers to one concave channel as the tunnel progresses rearward. The objective of the concave tunnel for which the '218 patent was to mount a motor higher on the transom of the boat, thus providing a shallow draft and minimizing propeller damage in shallow waters. This tunnel-hulled boat requires the additional use of sponsons to replace the buoyancy necessarily lost by implementing a tunnel into the tunnel-hulled boat. The '218 patent further requires relatively flat surfaces for the remainder of the hull of the boat such that the concave tunnel is merely one component of the overall hull design. It is thus an object of the invention to provide a sufficiently buoyant pontoon for which the entire running surface is generally concave, rather than merely having a localized concave tunnel as a feature of an otherwise rounded or flat pontoon.
U.S. Pat. No. 6,067,923 (the “'923 patent”), issued to Ratcliff, provides a hull configuration for a catamaran boat. The design of such hull is divided such that the forward two-thirds of each hull is V-shaped, which such V-shape being very pronounced at the front of the keel. Like the seaplane and the tunnel-hulled boat discussed above, the catamaran's hull tapers toward the rear, and the rear of the hull has a flat keel pad and flat lifting strake pads separated by ridges. Each ridge in the catamaran hull requires three distinct points at which the surface abruptly changes; these three angles adversely affect performance because the flow of water from the sharply angled ridge moves toward a different point than water moving over the flat keel, which generates turbulence. It is thus an object of the invention to provide a smoothly curved running surface which provides more lift for pontoon boats. It is thus an object of the invention to provide a large, smoothly curved, concave running surface for a pontoon such that the transition between running surface and lifting strake requires a minimum number of sharp angles.
The apparatus in accordance with the invention provides a concave pontoon that provides improved pontoon boat performance by maximizing lift and minimizing leakage by reducing weld length exposed to the water. The invention also provides reduced construction costs because it lowers the number of welds required to form a pontoon with lifting strakes.